We investigated whether hypnotizability, dissociation, and belief
in psi are related to performance in a precognition task that measures
whether later practice enhances previous memory recall. Participants low
(n = 19) and high (n = 19, 7 also high in dissociation) in
hypnotizability completed the task and a measure of belief in psi, with
the experimenters masked as to participants' level of
hypnotizability and dissociation. A general precognition effect was not
replicated and there was no overall effect for hypnotizability, but high
hypnotizables who were low in dissociation differed significantly from
dissociative high hypnotizables and from low hypnotizables, and scored
below chance. Belief in psi was related to dissociation and history of
trauma, and trauma and working memory were negatively correlated. With
respect to features of the experiment itself, we were contacted after we
bad run about one third of the participants by the developer of the
program, who asked us to use a modified version. We did not change our
protocol, but decided to analyze the data in segments before and after
we were asked to use a different program. Although not significant, the
first third of the data was clearly in the direction of psi-hitting
whereas later segments were in the opposite direction. A regression
analysis controlling for groups showed a significant decline effect. Our
results support the value of using selected groups and suggest that
dissociation may mediate the effects of hypnotizability in psi
performance.

Honorton and Ferrari (1989) conducted a meta-analysis of
precognitive experiments published between 1935 and 1987 and concluded
that there is experimental support for precognition and that it could
not likely be explained by real-time psi phenomena. A later series of
six experiments by Steinkamp (2003), however, reported inconsistent
support for a precognitive effect. Particularly relevant to this study
are the recent findings of Bem (2008a), who created the precognition
program and procedure we used in this study (Bem, 2008b). He reported
(Experiment 3; Bem, 2008a) significant results in support of
precognition, especially among participants scoring high in a measure of
novelty seeking. In this study we evaluated whether hypnotizability,
dissociation, and belief in psi affect performance on the precognition
test. We decided to use Bem's program to try to replicate his
previous studies and evaluate its usefulness in our sample.

PSI AND HYPNOTIZABILITY

Hypnotizability is a construct that refers to the extent to which
individuals follow and experience specific suggestions after a hypnotic
induction. It has been related to abilities such as imagery (Kogon et
al., 1998), fantasy-proneness (Lynn & Ruhe, 1986), absorption
(Tellegen & Atkinson, 1974), and experiential mental boundaries
(Cardena & Terhune, 2008). Considering the nature of these
correlates, the paucity of even moderate correlations between
hypnotizability and the "big five" personality traits, and the
finding that hypnotizability is related to the character trait of
self-transcendence, Cardena and Terhune (2008) proposed that the
propensity to have experiences that suggest personal unboundariedness
may be the latent trait underlying all of these correlations.

Kumar and Pekala (2001) reviewed studies that evaluated the
relationship between hypnotizability and anomalous experiences and
beliefs (including psi). Across 5 studies they found 11 correlations
between hypnotizability and paranormal belief, of which 9 were
significant (median r = .20). They found stronger results for
hypnotizability and paranormal experiences; 23 correlations, of which 20
were significant, were reported across 11 studies (median r = .31). They
also found 3 significant correlations across 2 studies for the relation
between imagery and psi experiences, (median r = .28) and 9 significant
correlations across 3 studies between absorption and anomalous
experiences as well as 8 significant correlations between
fantasy-proneness and paranormal experiences (median r = .36). As for
the relationship between these constructs and psi belief, they found
that 3 correlations in as many studies were significant (median r= .16).

Following an earlier meta-analysis by Schechter (1984), Stanford
and Stein (1994) reviewed the literature on the topic of hypnosis and
performance on controlled psi tests. The main question was whether psi
performance is better following a hypnotic induction than during a
control condition. The answer was positive, but no firm conclusions
about the cause of the effect could be drawn, as it was not clear
whether the induction per se or the difference in hypnotic abilities or
even an experimenter effect might have caused the differences in
performance. In an abstract, May, Banyai, Vassy, and Faith (2000)
reported no evidence between hypnotizability and psi performance in a
remote viewing experiment. However, Tressoldi and Del Prete (2007),
replicating the results of an earlier experiment, found significant psi
scoring in the first of two hypnotic sessions and significant small to
moderate correlations between successful psi performance and the
personality traits of absorption and transliminality, which have been
related to anomalous experiences and perhaps significant psi scoring.

Psi, DISSOCIATION, AND TRAUMA

Also of particular relevance is the trait of dissociation, which
refers to the propensity to have alterations of consciousness
characterized by detachment from self or others, or failures in the
integration of psychological processes that should ordinarily be
integrated (Cardena, 1994). Dissociative processes are sometimes assumed
or directly suggested in hypnotic performance and there have been
various proposals, harking back at least some decades (cf. White, 1937),
that there may be two distinct types of high hypnotizable individuals:
those who are mostly dissociative and do not exert imagery, and those
who are mostly imaginative (e.g., Barber, 1999; Barrett, 1990; Cardena,
1996).

Overall, there seems to be a stronger relation between dissociation
and psi experiences than between the latter and overall hypnotizability.
Re-analyses of data have shown that individuals exhibiting both high
dissociativity and high hypnotizability were more likely to report
anomalous (including putative psi) experiences than those with high
scores in either trait and much more so than those with low scores in
both of those traits (Pekala & Cardena, 2000, p. 71). Thus,
participants with high hypnotizability and high dissociation tend to
believe more in the paranormal and to report a greater number of
paranormal experiences than those who do not score high in both
variables. It bears mentioning, however, that dissociation is not
necessarily related to all types of unusual belief, such as those in
fantastic animals (Sharps, Matthews, & Asten, 2006).

With respect to the relationship between dissociation and actual
psi abilities, Cardena (1998) described various observed links between
the two, such as successful performance in psi tasks under dissociated
states, a link previously discussed by early psychic researchers such as
William James (e.g., Taylor, 1983) and the psychoanalyst Ferenczi. The
latter reported that a "traumatic trance" would not only
trigger dissociative mechanisms but also psi ("clairvoyant")
abilities because of the "timeless and spaceless omniscience"
(Ferenczi, 1955, pp. 162 and 243) occurring at the time of trauma,
abilities that might later be used to correctly evaluate and perhaps
escape further punishment and abuse (Ferenczi, 1955). Although not a
sufficient cause, there is a close association between acute or chronic
trauma and dissociation (Cardena, Butler, & Spiegel, 2003). That
chronically traumatized individuals might develop psi abilities could be
predicted by the psi-mediated instrumental response (PMIR) theory of
Stanford (1977), because psi information could help avoid distressing
events.

Irwin (1994a, 1994b) has reported that individuals who have a
history of early trauma tend to believe in psi phenomena and that the
latter belief is positively correlated with a tendency to dissociate. He
has explained these associations by positing that belief in psi and
paranormal events may be a psychological defensive mechanism constructed
to deal with the uncontrollability experienced early in life. Watt,
Watson, and Wilson (2007) corroborated Irwin's finding in a study
that found a negative association between paranormal belief and
perceived childhood control, although they cautioned that this
relationship explains only a small amount of the variance in belief in
reputed psi and paranormal events; they also corroborated that females
have stronger paranormal belief than men. A sophisticated analysis by
Lawrence, Edwards, Barraclough, Church, and Herrington (1995) tested
different models related to Irwin's hypothesis. They found that
although reported childhood trauma was associated with childhood
fantasy, which was related to reports of paranormal experience, there
was also a direct pathway between childhood trauma and paranormal
experience. They also confirmed that paranormal experience tends to give
rise to paranormal belief, rather than the other way around. Although
Lawrence et al. do not seem to have been aware of his work, their study
is the clearest general corroboration of Ferenczi's thesis that
trauma will directly give rise to paranormal experience, which is also
consistent with the proposal by Ring and Rosing (1990) that the
association between early abuse and propensity to have a near-death
experience can be explained by the alterations of consciousness first
experienced around the time of trauma.

To the best of our knowledge, no study has previously looked at the
interaction between hypnotizability, dissociation, and trauma in a psi
test. Cardena (2006) hypothesized that individuals high in fantasy or
those high in dissociation may perform differently according to the psi
tasks (e.g., those requiring good imaginative abilities such as the
ganzfeld protocol may be more suitable to high fantasy rather than high
dissociative individuals).

BELIEF IN PSI

One way to obtain more reliable results in psi experiments is to
identify which individuals may perform better in controlled experiments.
Schmeidler (1952) divided her participants in two groups, "sheep
and goats," on the basis of their belief in psi. Sheep are those
who believe in the possibility of psi in general or, more specifically,
in the experiment in which they were about to participate; goats have
the opposite expectation. The sheep-goat effect refers to the difference
in performance on a psi task between the two groups, where sheep have
been found to perform significantly better in psi tasks than goats,
especially when asked specifically about the psi task in consideration.
Under the hypothesis of no psi effects, of course, there should not be
any difference in psi tasks between the groups, provided that the tasks
prevented ordinary forms of information acquisition. Although the
sheep-goat effect is typically small, it has been consistently
replicated across studies. Lawrence (1993) reviewed 73 forced-choice ESP
studies with 37 principal investigators. He found a small but highly
significant sheep-goat effect; 24% of the studies found significant
results, in contrast to the expected 5% by chance. The effect size did
not covary with the study quality, so he reported a robust effect for
this relationship. As with all meta-analyses there is a risk for a
possible file-drawer effect (i.e., nonsignificant studies remaining
unpublished), although this seems unlikely given the paucity of research
in the area and the amount of "filed" studies that would be
needed to invalidate published findings. Thus, there is additional
reason to believe that, because they tend to believe more in psi, highly
hypnotizable and dissociative individuals may perform better in psi
tasks than those low in hypnotizability and/or dissociation (Kumar &
Pekala, 2001).

EXPERIMENTER EFFECTS

In all branches of science, some experimenters seem to be
consistently more successful than others in obtaining significant
results. In general there is a significant relationship between the
experimenter's actions on the task and the participants'
performance. Rosenthal (1966) has also discussed observer errors,
interpretation errors and fraud as potential artifacts in research.
Silverman, Shulman, and Wiesenthal (1972) found that different
experimenters obtained different responses from participants even on a
self-rating inventory. Silverman (1974) also conducted a survey to
investigate the numbers of experimenters in research. The sample
consisted of articles published in three APA journals between October
1968 and September 1969. Only 60 out of 300 studies included more than
one experimenter. In 20 cases it was just a matter of convenience with
no attention paid toward counterbalancing or measuring a possible
experimenter effect. A more recent survey in various disciplines
suggested that the use of "masked" methodology is very rare in
other disciplines than parapsychology (Sheldrake, 1998). Thus, despite
the evidence for experimenter effects, in practice not much attention is
given to this source of variance in research.

With respect to psi, Smith (2003a) found significant correlations
between psi-conduciveness, self-rated by researchers who had conducted
experiments, and reported beliefs in various aspects of psi. Both
psychological (e.g., how the experimenter interacts with the
participant) and parapsychological (e.g., the experimenter using his or
her own putative psi ability) factors may underlie the differences in
the data (Smith, 2003b). Wiseman and Schlitz (1997) examined the
experimenter effect by conducting a joint study in which a skeptic and a
proponent acted as experimenters for two sets of trials. In this
experiment electrodermal activity was used to measure whether
participants could detect remote staring. Participants who were run by
the proponent were significantly more physiologically reactive in stare
than nonstare trials compared to participants that were run by the
skeptic. The findings were replicated in a second study, but a third
experiment yielded nonsignificant results (Wiseman & Schlitz, 1999;
Schlitz, Wiseman, Radin, & Watt, 2006).

OUR STUDY

The purpose of this study was to examine whether hypnotizability,
dissociation, and belief in psi predict performance in a precognition
task. We evaluated the level of hypnotizability and dissociation, but no
hypnotic induction was conducted. Therefore, any differences between low
and high hypnotizable individuals would be caused by this trait and not
by a hypnotic procedure and its possible effect on the state of
consciousness. We also included as a variable belief in psi. Two
experimenters ran separate sets of trials and their belief in psi was
measured; thus another variable was the possible effect of the
experimenter that ran the sessions.

We had four hypotheses. The first one was that individuals would
remember more words to which they would be exposed again in the future.
The second was that high hypnotizables would perform better than lows in
the precognitive memory test. The third was that high hypnotizable, high
dissociators would perform better than the low dissociator highs. The
fourth was that belief in psi would correlate positively with
performance on the task.

METHOD

Participants

Participants in this experiment were recruited from a list of
people who had previously taken part in a hypnosis study and consisted
of those high or low in hypnotizability. The participants from each
group were spread out on different days for balancing purposes. The
experimenters were masked to group identity until the completion of data
collection. The number of participants was prespecified as N = 30
(Marcusson-Clavertz & Wasmuth, 2008) for completion of a thesis.
After those initial analyses were done, however, 8 additional
participants were recruited to increase the power of the study. For all
38 participants, age ranged from 19 to 65 years (M= 24.11, SD = 7.28).
There were 19 high hypnotizables (6 males, 13 females; [M.sub.age]=
23.21, SD = 2.25), 7 (6 females, 1 male; [M.sub.Age] = 24.00, SD = 2.00)
of whom also scored high in dissociation, whereas 10 scored low in
dissociation (5 males, 5 females; [M.sub.Age] = 23.00, SD = 2.49) and
there were no data on dissociation for the remaining 2 high
hypnotizables. We did not measure dissociation among the low
hypnotizables because we have found almost no low hypnotizables that
also score high in dissociation, as have other studies (e.g., Putnam,
Helmers, Horowitz, & Trickett, 1995). There were also 19 low
hypnotizables (11 males, 8 females; [M.sub.Age] = 25.00, SD = 10.11).
The participants were mainly Lund university undergraduates. All
participants gave informed consent to participate and were compensated
with a cinema ticket.

Experimenters

D. C. acted as the experimenter for 24 trials (12 high, 12 low)
whereas J. W. was the experimenter for 14 (7 high, 7 low) trials. The
experimenters were students and hold slightly different views on
parapsychology, with D. C. being more positive to the research in
general. J.W. had a more skeptical view but did not rule out the
possibility of psi phenomena. D. C. scored 14 out of 32 on the
Australian Sheep-Goat Scale (ASGS) and J. W. scored 8. The first author
of this paper is generally supportive of the psi hypothesis and scored
23 in the ASGS but did not interact with the participants.

Materials

Precognitive memory task. Precognitive memory was measured with a
computer program created by Bem (2008b). The program includes a
Filemaker database engine. The task was run on a PC computer in a
sound-attenuated room. In the task, participants first experienced a
3-min relaxation period in which they were shown Hubble images of the
galaxy accompanied by relaxing music. After the relaxation period we
asked the participants to visualize the referent to 48 English nouns,
shown in succession. The nouns came from four categories (foods,
animals, occupations, and clothes). Each word was presented for 3 s with
interstimulus intervals of 1 s. Next, participants were administered an
automated surprise recall test for which they were asked to recall as
many of the words as possible within a 5-min period. The recall test was
then followed by a practice session. Both the selection of practice
words and the practice session occurred following the completion of the
recall test; thus the participants could not know which words were
practice words at the time of the first recall test.

Half of the words from the original list were then randomly
selected and grouped into a list (the practice words). The remaining
half were not shown again and thus served as control words. The practice
words were divided into four lists with six words each. Each list
consisted of words from one of the four categories. The participants
were first exposed to one of these lists and asked to memorize the
words. When they clicked on the "ready" button, the list was
replaced by six empty slots for which the participants were asked to
fill in the correct words. If the participants forgot any of the words,
they had the opportunity to click on a button that revealed the list
again for a brief amount of time. This repetition could be done until
all slots were filled. The program did not monitor their answers at this
stage except that they had to at least write something in all six slots
before they were asked to recall six words from a category. When this
criterion was met and the participants clicked on an "OK"
button, the practice continued with the remaining three lists.

Australian Sheep-Goat Scale. The ASGS (Thalbourne & Delin,
1993) is a Rasch-scaled questionnaire with 16 items relating to belief
in psi phenomena. In this version two items relating to belief in
afterlife are excluded. Items consist of two bipolar statements. The
ASGS uses a visual analog scale; participants make a mark on a line
above the two statements. Items are scored from zero to two points,
depending on where the mark is placed. Total scores range from 0 to 32,
with greater scores reflecting increased belief in psi phenomena. The
18-item version of the ASGS was found to have strong test-retest
reliability (Thalbourne & Delin, 1993). The ASGS had good internal
consistency ([alpha] = .94) in this study.

Waterloo-Stanford Group Scale of Hypnotic Susceptibility (WSGC).
The WSGC (Bowers, 1993, 1998) is a group-version of the Stanford
Hypnotic Susceptibility Scale, Form C (SHSS:C; Weitzenhoffer &
Hilgard, 1962) and has strong psychometric properties (Bowers, 1993,
1998). The scale includes 12 dichotomously-scored suggestions including
ideomotor, challenge, and cognitive-perceptual suggestions. Scores range
from 0 to 12 and we defined those scoring 0-4 as low hypnotizables and
those scoring 8-12 as high hypnotizables.

Dissociative Experiences Scale (DES). The Swedish version (Korlin,
Edman, & Nyback, 2007) of the DES (Bernstein & Putnam, 1986;
Carlson & Putnam, 1993) is a 28-item scale with good psychometric
properties in which participants rate the percentage of time they
experience different dissociative phenomena. The final score reflects
the average percentage of the items. Individuals were categorized as
high dissociators if they scored above a cutoff value of 20.

Life Stressor Checklist-Revised. The LSC-R (Wolfe & Kimerling,
1997) is a valid and reliable 30-item questionnaire that assesses the
number and impact of various traumatic and adverse events throughout a
person's life. We used the number of checked items as the overall
score for this measure.

Procedure

The WSGC had been previously administered by either the first
author or another experimenter, Devin Terhune. The LSC-R had also been
previously filled out by 21 participants. For the next stage of the
study, volunteers were recruited for a study involving reading English
words and looking at faces (the latter for a different study). There was
no mention of psi or hypnotizability until the end of the experiment.
The consent form, however, mentioned that the purpose of data gathering
could not be revealed until the end of the experiment. Participants were
tested individually in laboratory sessions that lasted approximately 20
min. The instructions were to listen to the relaxation music and then
answer the English words test presented by the computer at the
participants' ease. The chair and the computer were arranged so
that they would be comfortable for each participant and lights in the
room were turned down, making the laboratory semidarkened. After the
completion of the task, the ASGS was administered to participants. At
the completion of data collection, participants were debriefed by e-mail
about the real purpose of the experiment and were provided with feedback
on how they had done on the precognitive test.

After about one third of our participants had been run, we were
contacted by the developer of the program, who suggested that we change
to a new version that included a slightly different practice test.
Because it was not practical to change programs at that point, we
decided instead to analyze the data in segments to ascertain whether
this new knowledge might affect the results; thus, before looking at the
results, we divided the data for the first 30 participants in thirds, to
which we added a fourth segment when we gathered additional data.

Statistical Analyses

Data were weighted; that is, the scores used were the difference
between the number of practice words recalled from the number of control
words recalled multiplied by the participant's overall score, to
control for total words recalled (Bem, 2008a). We used parametric tests
for analyses where all required assumptions were met and Kendall tau-b
coefficients to evaluate correlations between the DES and other
variables, given the nonnormal distribution of the DES reported in
previous research (Cardena, 2008b) and also observed in our data. We
assessed the effect of dissociation/ hypnotizability on other variables
through ANOVAs, planned comparisons and Tukey's HSD test. We also
conducted a regression analysis on the weighted scores to evaluate
performance across sessions. All analyses were done in SPSS (16.0). An
alpha level of .05, two-tailed was used for all statistical tests, and
Chauvenet's criterion (Taylor, 1997) was used to determine the
presence of any possible outlier, for exclusion from the relevant
analyses.

RESULTS

Demographic and Related Variables

We evaluated the correlations between age, sex, history of trauma,
belief in psi, dissociation, and number of words recalled. Belief in psi
had significant correlations with the tendency to dissociate, [tau](22)
= .53, p < .001, report more traumatic events, r(19) = .46, p = .04,
and with being female, r(36) = - .39, p = .02. History of trauma was
further associated with being older, r(19) = .62, p = .002 and with
fewer words recalled, r(19) = -.51, p = .02. The only other significant
correlation were between dissociation and history of trauma, [tau](19) =
.33, p = .04, and dissociation and being female, [tau](22) = -.35,p =
.04.

Age, sex, trauma history and belief in psi were not significantly
related to performance on the psi task (p >.3 for all analyses), so
these variables were not used further in analyses of the main dependent
variable. However, after we blocked the sample by dissociation we found
that the groups differed on their belief in psi, F(2, 32) = 5.48, p =
.009, [[eta].sub.p.sup.2] = .26. High hypnotizables who also scored high
in dissociation (henceforth "HdHys") exhibited stronger belief
in psi than low hypnotizables (henceforth "Lows"; M = 20.00,
SD = 4.86 vs. M = 8.89, SD = 8.15; planned contrast p = .002), and
marginally than high hypnotizables low in dissociation (henceforth
"LdHys"; M = 12.56, SD = 8.02; planned contrast p = .06).
There was no difference between Lows and LdHys (Tukey's HSD, p =
.47).

In replication of previous research, we found that having a history
of trauma, being more dissociative and hypnotizable, and being a female
were positively associated with believing in psi. We also replicated a
recent finding with adults that a history of trauma is related to poorer
working memory (El-Hage, Gaillard, Isingrini, & Belzung, 2006).
Taking the group as a whole, we did not replicate Bem's previous
research (Bem, 2008a), and contrary to what we hypothesized, neither
hypnotizability nor belief in psi as main effects predicted performance
on the precognitive memory test. However, the interaction of
hypnotizability and dissociation did produce significant results, with
the LdHys scoring worse than chance and lower than the other two groups,
which suggests that dissociativity may be a mediator of the possible
relationship between hypnotizability and performance in psi tasks. Other
areas in psychology (e.g., McFatter, 1994) have revealed that
interactions between traits have different or increased explanatory
power than the effect of those traits alone.

It is puzzling why LdHys psi-missed, as other research has found
hypnosis (rather than hypnotizability, though) to be associated with psi
scoring. A possible explanation is that we encountered a psi
differential effect, a phenomenon in which comparing contrasting
conditions produces one condition to score significantly better or worse
than chance, and the other one to have the opposite effect or none at
all (Irwin & Watt, 2007). We did not tell participants before
debriefing that they were participating in a psi test, so it might have
been that nonconsciously they misconstrued their task and recalled more
of the control than the practice words. A possible factor in the
psi-missing effect was the fact that we continued to use the same test
even after becoming aware that there might be a problem with it. This
might have created a negative psychological set in one or both
experimenters, somehow affecting more the LdHys, perhaps making them
less comfortable in the situation, a factor that Palmer (1997) has
discussed as a mediator of whether participants tend to psi-hit or
psi-miss. That the first third of the data was suggestive of psi-hitting
whereas the other segments reversed direction supports this hypothesis.

Low hypnotizables scored almost exactly at chance; HdHys also
scored at chance, contrary to our expectations, but the positive
correlation between trauma and dissociation, and the negative
correlation between trauma and recall suggests that psi memory tests may
not be ideal with this group. In any event, we think that further
research, especially with high hypnotizables, is warranted, although
they should be grouped by dissociativity as well. Bern (2008a)
recommended using individuals high in novelty seeking, and our
literature search did not reveal any studies evaluating a relationship
between novelty seeking and hypnotizability or psi beliefs or abilities.
A linear regression analysis on data of a group of alcohol dependents
showed that depression was not predicted by either novelty seeking or
self-transcendence (Evren, Sar, & Dalbudak, 2008). Because
self-transcendence is related to hypnotizability (Cardena & Terhune,
2008), the only data we know of suggests that novelty seeking is most
likely a different process than the ones we investigated in this study.

The data showed a decline effect, in accord with much of the
research in psi (cf. Irwin & Watt, 2007). Figure 2 suggests that the
effect was differential in that the group that was in the direction of
psi-missing at the beginning tended to improve, whereas the groups that
were in the direction of psi-hitting, followed the opposite pattern.
This seemed to be even clearer in the fourth stage of data collection,
after we had looked at the initial data. At that stage we obtained
outlier or near-outlier scores that went against the previous pattern.
Although by no means a test of von Lucadou's observation systems
theory, our results are consistent with it (cf. Lucadou, Romer, &
Walach, 2007).

Finally, although not significantly, we found some support for the
notion of an experimenter effect in that the experimenter with a
stronger belief in psi obtained scores in the direction of psi-hitting,
whereas the other experimenter got scores in the opposite direction.
However, the first experimenter was also the only one that showed a
significant decline effect. In any case, this study does suggest the
need to at least evaluate the effect of experimenters in a psi study.

This study had a number of limitations that should be acknowledged.
First, the N, especially after grouping, was modest, so the experiment
had limited power. Also, with small ns the significance of the data can
easily shift with inclusion of new data; thus our results should be
considered tentative and in need of replication. Another issue to
consider is that the task was completely in English and included words
that the participants were asked to visualize. In general, the words
were not very complicated but a few of them might have been difficult
for Swedish volunteers to understand (e.g., "mortician" and
"parka"). If the participants did not understand the words,
they would not have been able to visualize them. Hence, the way the
participants processed the words may have differed. Some may have
activated working rather than long-term memory. According to
Irwin's (1979) interpretation of Roll's memory trace theory,
that might have influenced how well the participants performed on the
test. It would therefore be optimal that additional studies using this
task be conducted in the participant's native tongue. The language
problem might have also depressed the scores of our other measures,
although probably not to a large degree (cf. Cardena, Kallio, Terhune,
Buratti, & Loof, 2007).

Second, it is possible that far from everyone gets relaxed by the
type of stimuli that the relaxation video included. For some
individuals, such relaxation could be associated with
traumatic/dissociative experiences and might have the opposite effect.
This question should be evaluated in future research. Also, there was a
constant humming sound coming from another computer in the room;
although the sound was fairly low, it might have served as another
distraction.

Another limitation might be the nature of the task. Presentiment
and other psi studies suggest that emotionality is an important factor
(Cardena, 2008a; Hinterberger, Studer, Jager, Haverty-Stacke, &
Walach, 2007). There was no emotional component in our task. It may
therefore be a good idea to expose the participants to stimuli of
greater salience in further experiments of this kind. Another issue
worth pursuing is to design a study with consequences that may be
desirable (or not) to the participants, as per Ferenczi's
hypothesis (1955) and the PMIR model (Stanford, 1977). And, as mentioned
earlier, memory tasks may not be ideal with individuals who are likely
to have more traumatic events in the past and to dissociate. The creator
of the task also mentioned to us (Bem, personal communication, August
2009) that the program as he had originally sent it to us did not
produce psi effects, as compared with other versions of the program,
which is why he had wanted us to modify it. This factor may have
affected the overall performance in the study, but it is worth pointing
out that we nonetheless obtained some significant effects when grouping
and when analyzing a decline effect.

In parapsychology the role of the experimenter has been emphasized
(Smith, 2003b); particularly the experimenter-participant interaction
has been brought into focus. Therefore the inexperience of the
experimenters and the way they interacted with the participants may have
affected the outcome of the study. Furthermore, both researchers had a
moderate score on the ASGS, which could have influenced the outcome as
well. It is hard to pinpoint exactly what experimental factors could
have made an impact on the outcome, as little is known about the
importance of personal characteristics in experimenters (Watt &
Wiseman, 2002). Although the program was developed to minimize the
experimenter role with the test being run mainly on computer, the
initial contact with the experimenter may still have an important role
to play in participants' performance.

Finally, hypnotizability may have had a greater effect in the
context of an actual hypnotic induction, as is suggested by reports of
an advantage of hypnosis over control conditions and of specific
hypnotic suggestions (Tressoldi & Del Prete, 2007; see also Cardena,
in press). Studies with and without a hypnotic procedure but also
measuring hypnotizability and dissociation should be conducted in the
future. In sum, we found a more complicated set of results than we had
originally predicted, but one pregnant with suggestions for future
research on the possible relationship between hypnosis, dissociation,
and psi.

SCHECHTER, E. I. (1984). Hypnotic induction vs. control conditions:
Illustrating an approach to the evaluation of replicability in
parapsychological data. Journal of the American Society for Psychical
Research, 78, 1-27.